I was happy till I started comparing myself to others. I was happy even in suffering, now I’m unhappy even in luxury. Society hinted to me that there’s a right kind of person, and this is the kind of person you should always look for outside of yourself. That success is a relative term, on a defined (and ever-increasing) base of comparison. And the parameters that make up this base are to be looked for in others. If someone you know has a total of 3 skills, you are unsuccessful if you have only 2; and hence, you are (or should be) unhappy. Every little part that you are made of has a kind of SI unit, a defined (near perfect) specimen that your part must be weighed against. It could be something as small as a nose, or as big as the colour of the skin that covers your whole body. Trying to be a good physicist and trying to reduce the error between the defined absolute and your measured imperfect value, you will forever be suffering.
To be happy, you just need your karma, dharma and santushti to be harmonised. Meaning what you do should satisfy you, without conflicting with your morals and sense of duty.